In a fiber to the distribution point (FTTdp for short) network, because it is difficult to feed power for a distribution point (DP for short) locally, how to supply power to the DP becomes a technical difficulty that needs to be solved in the FTTdp network.
In the prior art, power is supplied from internal power supply equipment (PSE for short) of a user home to an external DP of the user home, where a twisted pair is generally used as a medium for transmitting the supplied power. In such a power supply circuit, internal twisted pairs of a traditional user home are generally connected in series. If a power supply module is connected to a point on an internal line of the user home to reversely supply power to a DP, a voltage output by the power supply module not only is transmitted to the DP, but also is transmitted to other internal line interfaces of the user home. However, the other interfaces are generally connected to terminal devices such as an ordinary telephone set and modems of various digital subscriber lines. If the reverse voltage of this power supply module is transmitted to the terminal devices and no protective measure is taken by a user, some terminal devices may be burned out. Referring to FIG. 1, FIG. 1 is a schematic circuit diagram of supplying power to a DP in the prior art. In an internal cabling environment of a home, a first terminal device 100 and a second terminal device 200 are connected to a twisted pair. When a DP in an FTTdp network needs to be supplied with power, the DP is connected to the twisted pair, and a power supply module 300 is added so that the DP is conducted with the power supply module 300 through the twisted pair, thereby implementing reverse power supply for the DP. However, in addition to reversely supplying power to the DP, the power supply module 300 also transmits a reverse voltage to the first terminal device 100 and the second terminal device 200. Because the additional reverse voltage is introduced by the power supply module 300, there is a risk that the first terminal device 100 and the second terminal device 200 that are connected to the twisted pair may be burned out.